The processes that influence the movements of ions, especially heavy metals, across the lenticular membranes will be studied using an invitro preparation of the amphibian lens. This tissue is mounted in a divided chamber so that each side can be bathed by separate solutions, under which conditions ion fluxes across the anterior and posterior lens surfaces, as well as translenticularly, can be measured. A P.D. and short-circuit current which reflects ion movements can also be recorded across these membranes and their electrical resistance can be calculated. The immediate current aims are to continue a study of the effects of heavy metal ions on the lens, particularly with respect to understanding the processes that influence their uptake, accumulation and extrusion. An understanding of these mechanisms will include the use of drugs that can alter ion permeability, which in turn may suggest ways that such processes can be modified therapeutically. The ability of the lens to accumulate heavy metals and their ability to change the stability, conformation and structure of proteins suggests that such studies may not only provide information about the processes that normally control lens permeability but could also suggest mechanisms that could be involved in the genesis of senile cataracts.